The Multipath TCP protocol specification further outlines how a Multipath TCP connection can be established. According to this protocol, first, a single TCP connection between the client and server is established by a handshaking mechanism. During this handshaking mechanism, information on the capabilities and support for the Multipath TCP are exchanged. If one or both of the networking nodes do not support the MPTCP protocol, the connection is maintained as a single TCP connection. If both networking nodes support MPTCP, the client node may initialise a second handshaking mechanism for establishing a second TCP connection, i.e., a TCP subflow or auxiliary TCP connection.
A problem with establishing an MPTCP connection according to the above protocol is the time delay for establishing the subflows. For example, at least two 3-way handshakes must be performed for respectively establishing the first TCP connection and then the auxiliary TCP connection. That means that at least six messages are exchanged before the MPTCP connection is fully operable and thus before the full bandwidth of the two connections can be used to transfer data. This is especially disadvantageous in situations where connections have a limited lifetime within which data must be transferred as fast as possible. This is for example the case for browsing applications and the connections established with web services by such applications.